1. Field of the Invention
The present invention relates to an ink receiver for capturing the preliminary discharge of ink, and an ink-jet recording apparatus and method for preliminary discharge of ink through ejection holes of the recording head using that receiver.
2. Description of the Related Art
An ink-jet recording apparatus is a type of recording apparatus which effects recording by ejecting ink from a recording head onto a recording medium such as paper. A recording apparatus of this type includes, in addition to a structure directly related to the recording function, an inherent structure for maintaining ink in a stable condition that is fit for ejection.
Since recording data vary, ink may not be ejected through one or more ejection holes for a relatively long period of time, and it is also possible that the entire recording apparatus may not be used for a long period of time. In such cases, some of the water in the ink stored at the ejection holes or within an ink chamber communicating with the ejection holes may evaporate, causing the viscosity of the ink in the apparatus to increase. As a result, ink may not be ejected when necessary. In addition, since the surface of the recording head on which the ejection holes are formed may have ink droplets, ink mist, water droplets and/or dust adhered thereto, the adhered substances may cause, during ejection, ink droplets to be ejected in a direction deviating from the desired direction(s).
In order to avoid these problems, the typical ink-jet recording apparatus has a system, known as an ejection recovery system, for preventing such ejection failures and deviations in the direction of ejection, and thereby maintains the ink in a stable condition fit for ejection through the ejection holes.
Such ejection recovery systems can be of varying construction. For example, an ejection recovery system may be constructed to prevent improper ejection by employing preliminary discharge, ink-suction recovery, ink-pressurization recovery and/or capping. In preliminary discharge, ink is discharged to a certain ink receiver to thereby remove the viscous ink portion, etc. In ink-suction recovery, such removal is effected by using a pump to draw ink out from the ejection holes and the ink chamber. In ink-pressurization recovery, removal is effected by using a pump to pressurize ink so as to force ink out from the ejection holes and the ink chamber. In capping, the surface of the recording head formed with the ejection holes is tightly covered by a cap during the non-recording period so as to prevent the water contained in the ink from evaporating through the ejection holes.
Designing an ink-jet recording apparatus, particularly a small and inexpensive one, involves overcoming many problems.
The main source of these problems is the ejection recovery system. Specifically, reducing the size of the apparatus is limited by the fact that a certain amount of space is necessary to provide devices for preliminary discharge, ink-suction recovery, ink-pressurization recovery and/or capping. Reducing the size of the apparatus is also affected by the need to have space for other related devices such as a waste ink tank for storing waste ink removed by preliminary discharge, suction, etc., and a suction pump and tubes for guiding waste ink into the waste ink tank.
The ejection recovery system has been inevitably very large, especially in the case of an ink-jet recording apparatus adapted for color recording by employing four colors of ink, yellow, magenta, cyan and black. When the ink-jet recording apparatus is the type having independent recording heads for the individual inks, caps, tubes, pumps, and like devices have been provided correspondingly.
However, when independent caps corresponding to the individual recording heads are provided, the positional relationships between the different caps and the corresponding heads may have various levels of precision. As a result, when the caps are brought into contact with the recording heads, tight contact may not be provided as desired.
Such an ink-jet recording apparatus may have a single recording head in which a plurality of groups of ejection holes, for example, four groups of ejection holes for yellow, magenta, cyan and black inks, are formed. A recording head with this construction is advantageous in that it does not require registration between the plural groups of ejection holes, and in that the head has high precision of nozzle pitch, thereby enabling high-quality recording.
When this recording-head construction is adopted, however, the distance between two adjacent groups of ejection holes cannot be increased beyond the limits achievable by various manufacturing processes. The inter-group distance is, for example, 1 mm, which is a relatively small dimension. When the inter-group distance is increased in spite of manufacturing process limitations, the surface of the recording head with the ejection holes formed therein may become too long to maintain a prescribed gap between the surface of the recording head having ejection holes therein and the recording medium such as paper. Thus, it is inappropriate to increase the distance between the groups of the ejection holes.
When such a single recording head is combined with a plurality of caps corresponding to the individual groups of ejection holes for the purpose of achieving tight head-cap contact, the relatively short distance between two adjacent groups makes it difficult to simultaneously bring the outer wall portions of two adjacent caps into tight contact with an inter-group portion of the recording head. As a result, an ink sucking operation may not be performed properly.
In order to overcome this problem, some of the caps and other related devices may be provided in common. However, the adoption of this arrangement may involve the following problems:
10 During the replacement of an ink tank holding one of several colors of ink, an ink sucking operation is performed to remove bubbles which have entered into the path between the ink tank and the recording head, as well as to prime the recording head with ink from the ink tank. In this operation, however, ink is simultaneously sucked from both the ejection holes connected with the relevant ink tank and the ejection holes connected with other ink tanks by paths which need not be cleared. As a result, the total amount of waste ink increases over the amount produced by an ejection recovery system with no common elements. Some ink in the ink tanks not meant to be cleared has to be wasted, and the increased total volume of waste ink requires use of a larger waste ink tank. It is very important to achieve a high efficiency of ink use particularly in a small apparatus which cannot be equipped with a large ink tank device.
2 When ink is being cleared, other bits of ink adhering to the vicinity of the ejection holes of the recording head after ejection therethrough are diffused in the flow of ink being cleared, causing ink of a color having a relatively high density, such as black ink, to be mixed with ink of a color having a relatively low density, such as yellow. The thus-formed mixture may enter ejection holes for an ink having a relatively low-density color, such as yellow. As a result, a mixed color ink, which is darker than the yellow ink that should be ejected, may be ejected in actual recording.